Updated "POST /containers/create" to return the right Content-Type.
Added a status code argument to writeJSON.
Rebased.
Replaced leading spaces with tabs.
Updated postContainersCreate to use writeJSON.
Replaced leading spaces with tabs. Again.
Fixed a bug I created when rebasing.
Merge pull request #1726 from dsissitka/1615-2

Updated "POST /containers/create" to return the right Content-Type. Fixes #1615.